The objective is to develop a fiber optic-based, real-time, in-situ method for distinguishing bone from polymethyl methacrylate (PMMA) cement during replacement hip arthroplasty surgery. The proposed method is based on near-infrared (NIR) spectroscopy, which has been shown to be a viable method for distinguishing bone and PMMA in the laboratory. The program is designed to test the usefulness of the method under realistic conditions. Bone-PMMA models will be prepared using cadaver femurs and PMMA- cemented components, and fiber-optic NIR spectroscopy will be used to obtain sets of spectra across the bone-PMMA composite surfaces to determine the extent to which the materials can be uniquely identified under a variety of realistic working conditions. Changes in the spectra will be interpreted for correlation with changes in, e.g., the nature of the fluid bathing the sample. Statistical methods (chemometrics) will be used to build a predictive model based on the spectra, and the model will be tested for accuracy in determining the bone/PMMA distribution in additional samples. The development of a quick, accurate method for distinguishing bone from PMMA cement during surgery is expected to facilitate the removal of PMMA during replacement hip arthroplasty, an operation that is performed over 40,000 times a year in the United States. [unreadable] [unreadable] [unreadable]